This invention relates generally to ceramic articles, processes for imprinting such articles and imprinting apparatus and, more particularly, to a ceramic article, process and apparatus for imprinting a ceramic article using a sublimation heat transfer technique.
Sublimation heat transfer techniques for imprinting metal, especially aluminum, articles and textiles are well known. In general, sublimation heat transfer techniques require use of a sublimable dye incorporated on or in a suitable carrier. The carrier is affixed to a substrate and heat is applied in order to cause the dye to sublime into the substrate. In some instances, it is necessary to apply pressure in addition to heat in order to effect the sublimation transfer.
A sublimable dye is a dye that passes directly from a solid state to a gaseous state under proper conditions of temperature and pressure. The use of such dyes are discussed, for example, in U.S. Pat. No. 4,201,821 issued to Fromson et al on May 6, 1980, which also gives formulas for a number of such dyes.
Fromson et al relates to a method for decorating anodized aluminum with a design or image by a sublimation heat transfer process. The anodized aluminum substrate is coated with a porous unsealed anodic oxide layer and then with a polymeric material that is substantive to a sublimable dye. The carrier containing the sublimable dye is contacted with the polymeric material and heated for a period of time sufficient to cause the dye to sublimate and condense in the oxide layer and the polymeric material. Although not specifically stated, Fromson et al presumes that the anodized aluminum substrate provides a flat surface. A similar process is discussed in U.S. Pat. No. 4,177,299 issued to Severus et al on Dec. 4, 1979 wherein it is disclosed that optimum results are obtained when the oxide layer has a thickness between about 5 and 25 .mu.m.
U.S. Pat. Nos. 4,465,489 issued Aug. 14, 1984 and 4,591,360 issued May 27, 1986 both to Jenkins et al disclose a method of decorating curved metal containers by providing the containers with a coating that is receptive to a sublimable dye. The receptive coating is a non-linear, cross-linked polyester or non-linear, cross-linked thermosetting acrylic resin. Epoxy polyester, polyester, polyester epoxy, alkyd, alkyd-melamine, acrylic, acrylated and acrylated acrylic are cited as suitable coating materials. A suitable sublimable dye on a carrier such as paper is secured to the coating material using a water-soluble adhesive. Heat is applied and the sublimable dyestuff is transferred into the coating layer through the adhesive. Then the carrier is removed using water.
An apparatus and method for printing cans from heat transfer paper are disclosed in U.S. Pat. Nos. 4,250,831 issued on Feb. 17, 1981 and 4,323,601 issued on Apr. 6, 1982 both to McMillan et al. The cylindrical cans or members are continuously rolled along the apparatus and heat transfer sheet material is wrapped around the cylindrical member. Heat is provided to cause the image to be transferred from the sheet material to the cylindrical member and then the carrier is unwrapped from the member. This is not suitable for use with mugs as the mug handle prevents the cylindrical member from being rolled.
In contrast, a traditional ceramic glazing process is shown in U.S. Pat. No. 1,334,301 issued to Hasburg on Mar. 23, 1920. As disclosed in the Hasburg patent, ceramic ware is glazed with a glaze that will take a stain and auxiliary glaze metallic salts or bases mixed with a clay material are applied. The ceramic ware is burned to develop the color by fire. The burned colored portion of the ceramic ware is then reglazed with a clear secondary glaze that must be fired. Such a process has the disadvantages that it is extremely time consuming and suitable equipment such as kilns or lehrs must be available for heating the glaze at temperatures up to about 1000.degree. F. for an extended period of time.
Alternatively, ceramic mugs can be imprinted using special screen printing equipment and ceramic ink. Each article must then be dried or cured using a tedious and time consuming process that does not permit the production of large quantities of articles in a short period of time. Furthermore, recent revisions to Federal Occupational Safety and Health Administration (OSHA) requirements regarding the composition and safety standards for printing inks have had a deterrent effect on use of this process to produce ceramic mugs. Finally, any deviation from the strictest standard of care in producing these products will prevent the image from being dishwasher safe.
In another prior art method, a special type of decal known as an electrocal decal is applied in a production line requiring use of a kiln or oven. Most quality ceramic mugs are imprinted by this method, but the method is most suitable for production of large quantities of mugs of a single design or graphic. The process of baking and cooling each item can take as long as a day, representing a limitation on the number of articles produced and even the simplest kiln is expensive and unwieldy. Moreover, such a process requires preselection of the image and makes the production of small number of mugs very costly.
Accordingly, it is desirable to provide a ceramic article, process for imprinting such articles and an imprinting apparatus that overcomes the aforenoted disadvantages of the prior art.